The pthread_attr_setschedparam() function sets the scheduling
parameter attributes of the thread attributes object referred to by
attr to the values specified in the buffer pointed to by param.
These attributes determine the scheduling parameters of a thread
created using the thread attributes object attr.
The pthread_attr_getschedparam() returns the scheduling parameter
attributes of the thread attributes object attr in the buffer pointed
to by param.
Scheduling parameters are maintained in the following structure:
struct sched_param {
int sched_priority; /* Scheduling priority */
};
As can be seen, only one scheduling parameter is supported. For
details of the permitted ranges for scheduling priorities in each
scheduling policy, see sched(7).
In order for the parameter setting made by
pthread_attr_setschedparam() to have effect when calling
pthread_create(3), the caller must use
pthread_attr_setinheritsched(3) to set the inherit-scheduler
attribute of the attributes object attr to PTHREAD_EXPLICIT_SCHED.

pthread_attr_setschedparam() can fail with the following error:
EINVAL The priority specified in param does not make sense for the
current scheduling policy of attr.
POSIX.1 also documents an ENOTSUP error for
pthread_attr_setschedparam(). This value is never returned on Linux
(but portable and future-proof applications should nevertheless
handle this error return value).

This page is part of release 4.08 of the Linux man-pages project. A
description of the project, information about reporting bugs, and the
latest version of this page, can be found at
https://www.kernel.org/doc/man-pages/.
Linux 2015-08-08 PTHREAD_ATTR_SETSCHEDPARAM(3)